1. Field of the Invention
The present invention relates generally to spindle motors for use in disk drives, and more particularly to a spindle motor having a stator rim formed of curved arc segments.
2. Description of the Prior Art
The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA) having an actuator assembly having at least one transducer head, typically several, for reading and writing data to and from the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to tracks disposed upon the disk.
The head stack assembly includes an actuator assembly, at least one head gimbal assembly, and a flex circuit cable assembly. A conventional xe2x80x9crotaryxe2x80x9d or xe2x80x9cswing-typexe2x80x9d actuator assembly typically comprises an actuator body that rotates on a pivot assembly between limited positions, a coil portion that extends from one side of the actuator body to interact with one or more permanent magnets to form a voice coil motor, and one or more actuator arms which that extend from an opposite side of the actuator body. A head gimbal assembly includes at least one transducer head, sometimes two, which is distally attached to each of the actuator arms. The actuator assembly includes the actuator body that has a bore and a pivot-bearing cartridge engaged within the bore. The at least one head gimbal assembly and the flex circuit cable assembly are attached to the actuator assembly.
The spindle motor includes a hub that is rotatably attached to the disk drive base. The hub has an outer flange that supports one of the disks. Additional disks may be stacked and separated with spacers. The spindle motor further includes an annular magnet element and a spindle motor stator. Where space efficiency is of vital concern, the magnet element is typically attached about the lowermost portion of the hub below the flange. The magnet element consists of a predetermined number of N and S poles that are disposed alternately circumferentially about the magnet element. The spindle motor stator includes an outer stator rim that is attached to the disk drive base and a plurality of internally facing stator teeth. The stator teeth are equally spaced and extend from the stator rim. The spindle motor stator is sized to fit about the hub and in particular the magnet element. Windings are oriented vertically about each of the stator teeth. The windings selectively conduct current to create a magnetic field that interacts with the various poles of the magnet element. Such interaction results in forces applied to the hub which tend to rotate the hub. In those disk drives capable of reading both sides of the disks, the head stack assembly includes an actuator arm that extends and pivots between the vertical region between the lowermost disk and the spindle motor stator.
A topic of concern is the desire to reduce the overall disk drive size. Such disk drives may have a variety of applications such as in hand held or portable electronic devices. The exterior size and shape of the disk drive is often referred to as a xe2x80x9cform factor.xe2x80x9d Reduction of such disk drive form factor has proven challenging. This is because the mere reduction of the size of the various disk drive components may result in such components being unable to conform to required specifications.
One particular area of focus is the reduction of the height of the disk drive. As mentioned above, a prior art arrangement includes a lower actuator arm which extends and pivots between the vertical region between the lowermost disk and the spindle motor stator. Such prior arrangement is contemplated to be a limited factor in the overall sizing of the disk drive height. The mere reduction in vertical sizing of the spindle motor and its magnet element would directly reduce the total flux associated with the spindle motor which may be below acceptable specifications. Accordingly, there is a need in the art for a reduced height-to-diameter ratio spindle motor configuration which generates sufficient torque to meet acceptable specifications in comparison to the prior art.
An aspect of the invention can be regarded as a spindle motor for use in a disk drive. The spindle motor includes a spindle motor hub having an axis of rotation. The spindle motor further includes an annular magnet element coupled to the spindle motor hub. The spindle motor further includes a spindle motor stator. The spindle motor stator includes a stator rim formed of a plurality of adjacent arc segments. The arc segments each respectively has opposing curved ends extending parallel to the axis of rotation. The curved ends of respective adjacent arc segments cooperatively form a plurality of stator teeth in operable communication with the magnet element for rotating the spindle motor hub. The spindle motor stator fturther includes a plurality of windings distributed along the stator rim. The windings each have a winding axis parallel to the axis of rotation and being disposed about respective ones of the stator teeth.
In an embodiment, each of the stator teeth has a magnetic flux surface disposed with the associated winding axis extending orthogonally from each magnetic flux surface. The magnet element may be disk-shaped. In another embodiment, each of the stator teeth has a magnetic flux surface with the associated winding axis extending parallel to each magnetic flux surface. The magnet element may be disposed concentrically about the stator teeth or the stator teeth may be disposed cooperatively about the magnet element. The magnet element may further be cylindrical-shaped or ring-shaped. Each of the arc segments may be formed of at least two laminate layers, and the laminate layers are stacked along the axis of rotation.
In additional embodiments of the present invention, there are provided disk drives each having a disk drive base. The above-mentioned spindle motors may be included the disk drives as attached to the disk drive bases.